Bending device for bending plastically deformable strip material

ABSTRACT

The invention relates to a bending device ( 1 ) for bending plastically deformable strip material ( 15 ). According to the invention, the reverse bending that is required for workpieces with narrow processing tolerances in particular takes place independently of the actual bending. This increases the processing precision of the workpieces and simplifies the numerical control of the device. The reverse bending unit ( 11 ) is moveably arranged on the bending unit ( 9 ) in the bending device ( 1 ).  
     Es wird eine Biegevorrichtung ( 1 ) zum Biegen von plastisch verformbarem Bandmaterial ( 15 ) vorgeschlagen, bei der die insbesondere bei Werkstiücken mit engen Fertigungstoleranzen erforderliche Rückbiegung unabhängig von der eigentlichen Biegung erfolgt. Dadurch kann die Fertigungsgenauigkeit der Werkstücke erhöht und die numerische Steuerung der Vorrichtung vereinfacht werden. In der Biegevorrichtung ( 1 ) ist die Rückbiegeeinheit ( 11 ) an der Biegeeinheit ( 9 ) bewegbar angeordnet.

[0001] Bending Device for Bending Plastically Deformable Strip MaterialThe invention relates to a bending device for bending plasticallydeformable strip material, having an advance unit, a guide unit and abending unit, where the bending unit has a bending roller and a reversebending unit.

[0002] This bending unit is known from DE-OS 198 16 609 A1. It is usedfor bending sections of strip material which can be used to produceflat-blade windshield wipers. The bending unit of this known bendingdevice consists essentially of several locating points through which thestrip material to be bent is guided. Depending on the desired bendingradius, the relative position of the locating points to each other ischanged. In order to obtain high-precision bent parts, it is necessaryto reduce the residual stress created in the strip material duringbending by controlled reverse bending and thus ensure the formalaccuracy of the work piece during operation. The reverse bending unit ofthe known bending unit consists essentially of a bending roller whoserelative position to the bending unit can be altered, so that reversebending can be adjusted to the desired degree.

[0003] The disadvantage of this bending device is that the position ofthe reverse bending unit depends both on the position of the bendingunit as well as on the desired degree of reverse bending. Theconsequence of the dependence of the position of the reverse bendingunit on the bending unit is that, even with constant reverse bending butchanging initial bending, the reverse bending unit has to be controlledto match the change in the bend. If both bending and reverse bending areto be changed during the bending process, both the above dependencieshave to be taken into consideration when controlling the position of thereverse bending unit. Coupling the bending and reverse bending processescan have negative effects on the quality of the work pieces and inaddition requires great expense on the machine and the control side.

[0004] The object of the invention is to prepare a bending device forbending plastically deformable strip material with which the work piecescan be produced to the highest quality and which is nevertheless simplyconstructed and simple to control.

[0005] This object is achieved under the invention by a bending devicefor bending plastically deformable strip material, having an advanceunit, a guide unit, a bending unit with a reverse bending unit, wherethe relative position of the reverse bending unit to the bending unit isadjustable and where the reverse bending unit is mounted moveably on thebending unit.

[0006] As a result of the inventive positioning of the reverse bendingunit on the bending unit, it is possible to keep the reverse bending, orthe reverse bending torque respectively, constant when the bend ischanged during the bending process with little expense for controlequipment, since the reverse bending unit also performs the adjustingmovements for the bending unit. If the reverse bend is to be changedduring the bending process, it is only necessary to move the reversebending unit relative to the bending unit, so that compared with theknown bending unit a decoupled, simpler and more precise control of thereverse bending unit is achieved.

[0007] In one version of the bending unit under the invention, provisionis made for the bending unit to have a bending roller and for thereverse bending unit to be rotatable about the axis of rotation of thebending roller, so that the reverse bending unit is mounted to thebending unit with a simple, economical and accurate pivot bearing.

[0008] To improve the invention the bending unit can be moved slidinglyrelative to the guide unit, so that different bending radii arepossible.

[0009] In one embodiment of the invention the position of the bendingunit is controlled relative to the guide unit, specifically numericallycontrolled, so that a change in the bending radius is possible duringthe bending process.

[0010] In another embodiment of the invention the rotation of thereverse bending unit around the axis of rotation of the bending rolleris controlled, specifically numerically controlled, so that the reversebend can also be changed during the bending process.

[0011] In an improvement of the invention, the reverse bending unit hasa crank on which a reverse bending roller is located, resulting insimple construction of the inventive bending device, capable ofsustaining a high mechanical load.

[0012] In a further improvement of the invention, the distance of thereverse bending roller to the axis of rotation of the bending roller isadjustable so that a further degree of freedom is attained in shaping ofthe reverse bending process.

[0013] In other embodiments of the invention provision is made for anactuator to rotate the reverse bending unit at least indirectly,specifically for a pneumatic cylinder, a hydraulic cylinder, a linearmotor or a servo motor to be provided so that the reverse bending unitcan be rotated depending on the required accuracy of positioning.

[0014] In one embodiment of the invention a pinion is furnished on thereverse bending unit, whose center lies in the axis of rotation of thebending roller and the actuator drives a rack interacting with thepinion so that, independently of the rotational position of the reversebending unit, the force of the actuator is proportional to the torqueexerted by the reverse bending on the strip material. A constant reversebending torque can thereby be set in a very simple way.

[0015] In another embodiment of the invention the actuator isarticulated at a point outside the rotational axis of the bending rolleron the reverse bending unit so that control of the reverse bending unitis simple and economical.

[0016] Another embodiment envisions that a servo drive is provided asthe actuator.

[0017] In one embodiment of the invention the guide unit has severalguide rollers positioned on both sides of the strip materials so thataligning and guiding the strip material involves low-friction and iseconomical and operationally safe.

[0018] As an improvement to the invention provision is made for theadvance unit to have at least two advance rollers positioned on oppositesides of the strip material and for at least one advance roller to bedriven by a motor, so that the strip material can be transported throughthe bending unit in a simple way. The drive for the advance unit can benumerically controlled.

[0019] In a further improvement to the invention, provision is made fora cutting unit, also numerically controlled, so that after a workpieceis completed it can be separated from the strip material.

[0020] In a further improvement of the invention, a reader is furnishedwhich sends signals to the bending device controls depending on markingson the strip material so that no serial failures occur in the productionof work pieces from the strip material.

[0021] Other advantages and advantageous embodiments of the inventioncan be found in the following description, the drawing and the claims.

[0022] One embodiment of the subject of the invention is shownschematically in FIG. 1.

[0023] A schematic rendering of the bending device 1 under the inventionis shown in FIG. 1. It consists of an advance unit 3, a reader 5, abending unit 9 and a reverse bending unit 11.

[0024] The advance unit 3 consists of two advance rollers 13 betweenwhich strip material 15 runs, which is coiled on a supply spool 17. Theadvance rollers 13 are driven and exert a contact pressure on the stripmaterial 15 so that the advance pressure is transferred frictionallyfrom the advance rollers 13 to the strip material 15. Not shown in theFigure is a numerical control for the bending device 1 which alsocontrols the advance unit 3. Also not shown are trigger markings on thestrip material 15 which mark the beginning and/or end of a workpiece.Also not shown in the Figure are possible changes to the width and/ordepth of the cross section of the strip material 15, which providedifferent degrees of bending stiffness.

[0025] Viewed in the pass-through direction of the strip material 15, areader 5 is located behind the advance unit 3, which recognizes thetrigger markings on the strip material 15 not shown in the Figure andtransmits corresponding signals to the controls for the bending device1. By triggering the controls with the strip material 15, serialfailures are avoided and thus the precision of the finished bent part isenhanced.

[0026] A guide unit 7 is attached in sequence to the reader 5,consisting of several rotatably mounted guide rollers 19. The guiderollers 19 are positioned on both sides of the strip material 15 andensure that the strip material 15 enters the bending unit 9 in aspecific direction and that torque occurring during bending isdissipated.

[0027] The bending unit 9 has a bending roller 21 with a rotational axis23. The bending roller 21 is positioned on a carriage 25, which in turncan be moved slidably in the direction of the double-ended arrow 27. Thebending radius of the strip material 15 is determined by sliding thecarriage 25. The carriage 25 is moved by a positioning cylinder 29.Naturally, gear motors with jack screws, linear motors or similar aresuitable for effecting the movement of the carriage 25. The positioningcylinder 29 is controlled by the controls for the bending device 1.

[0028] The reverse bending unit 11 has a rotatably mounted crank 31,where the rotational axis of the crank 31 and the rotational axis of thebending roller 21 coincide. On the crank is a reverse bending roller 33whose rotational axis runs parallel to the rotational axis 23 of thebending roller 21. The reverse bending roller 33 is attached moveably inan elongated hole 35 on the crank 31 so that the distance betweenreverse bending roller 33 and the bending roller 21 is adjustable. Thisresults in an additional degree of freedom in the shaping of the reversebend.

[0029] A contact point 37 between reverse bending roller 33 and stripmaterial 15 lies on the other side of the strip material 15 as does acontact point 39 between bending roller 21 and strip material 15.

[0030] Concentric to the rotational axis 23, a pinion 41 is securedagainst rotation on the crank 31, which a rack 43 engages which can beslid by an actuator 45 in the direction of the double-ended arrow 47.The actuator 45 is also controlled by the controls for the bendingdevice 1, which are not shown. An adjusting motion of the actuator 45effects a rotational motion of the crank 31 about the axis of rotation23. Any desired reverse bending torque can thus be set by rotating thecrank 31.

[0031] The advantage of this embodiment is that, assuming constantpressure, or constant adjusting force respectively, from the actuator45, the reverse bending torque that is transmitted by the reversebending roller 33 to the strip material 15 is independent of theposition of the carriage 25 or of the bending torque which the bendingroller 21 exerts on the strip material 15. Bending and reverse bendingare thereby completely decoupled from each other, which improves theprecision of the shape of the bent work pieces on the one hand and onthe other simplifies the controls for the bending device under theinvention.

[0032] In another embodiment which is not shown in FIG. 1, a piston 49on the actuator 45 is articulated directly to the crank 31 so that aparticularly simple and economical rotation of the crank 31 is possible.In this embodiment an additional non-linear connection exists betweenthe position of the actuator and the torque transmitted by the reversebending roller 33 to the strip material 15. Since this nonlinearconnection is positive, the reverse bending torque can be adjustedprecisely through the controls for the actuator 45.

[0033] Also not shown in the Figure is a cutting unit with which acompletely processed work piece is separated from the strip material 15,whereupon production of the next workpiece can begin.

[0034] The bending unit under the invention is particularly suitable forbending the backbones of flat-blade windshield wipers, embodimentswhereof are described in U.S. Pat. No. 3,192,551.

[0035] All the features shown in the description, the subsequent claimsand the drawing can be fundamental to the invention both individually aswell as in any combination with each other.

[0036] List of Reference Numerals

[0037] 1 Bending device

[0038] 3 Advance unit

[0039] 5 Reader

[0040] 7 Guide unit

[0041] 9 Bending unit

[0042] 11 Reverse bending unit

[0043] 13 Advance roller

[0044] 15 Strip material

[0045] 17 Supply spool

[0046] 19 Guide roller

[0047] 21 Bending roller

[0048] 23 Rotational axis

[0049] 25 Carriage

[0050] 27 Double-ended arrow

[0051] 29 Positioning cylinder

[0052] 31 Crank

[0053] 33 Reverse bending roller

[0054] 35 Elongated hole

[0055] 37 Contact point between reverse bending roller and stripmaterial

[0056] 39 Contact point between bending roller and strip material

[0057] 41 Pinion

[0058] 43 Rack

[0059] 45 Actuator

[0060] 47 Double-ended arrow

[0061] 49 Piston

What is claimed is:
 1. Bending device for bending plastically deformablestrip material (15), having an advance unit (3), a guide unit (5), abending unit (9) and a reverse bending unit (11), where the relativeposition of the reverse bending unit (11) to the bending unit (9) isadjustable, characterized in that the reverse bending unit (11) isarranged moveably on the bending unit (9).
 2. Bending device from claim1, wherein the bending unit (9) has a bending roller (21) and thereverse bending unit (11) can be rotated about the rotational axis (23)of the bending roller (21).
 3. Bending device from claim 1 or 2, whereinthe bending unit (9) can be slid relative to the guide unit (7). 4.Bending device from claim 3, wherein the position of the bending unit(9) is controlled, specifically numerically controlled, relative to theguide unit (7).
 5. Bending device from one of the preceding claims,wherein the rotation of the reverse bending unit (11) about therotational axis of the bending roller (21) is controlled, specificallynumerically controlled.
 6. Bending device from one of the precedingclaims, wherein the reverse bending unit (11) has a crank (31), andwherein a reverse bending roller (13) is arranged on the crank (31). 7.Bending device from claim 6, wherein the distance of the reverse bendingroller (33) to the rotational axis (23) of the bending roller (21) isadjustable.
 8. Bending device from one of the preceding claims, whereinan actuator (45) arranged on the bending unit (9) is provided, rotatingthe reverse bending unit (1) at least indirectly.
 9. Bending device fromclaim 6, wherein the actuator (45) is a pneumatic cylinder, a hydrauliccylinder or a linear motor.
 10. Bending device from claim 9, wherein apinion (41) is furnished on the reverse bending unit (11), the center ofthe pinion (41) lies in the rotational axis of the bending roller (21),and the actuator (45) drives a rack (42) interacting with the pinion(41).
 11. Bending device from claim 9, wherein the actuator (45) isarticulated at a point outside the rotational axis (21) of the bendingroller (21) on the reverse bending unit (11).
 12. Bending device fromclaim 8, wherein the actuator (45) is a servo drive.
 13. Bending devicefrom one of the preceding claims, wherein the guide unit (7) has severalguide rollers (19) arranged on both sides of the strip material (15).14. Bending device from one of the preceding claims, wherein the advanceunit (3) has at least two advance rollers (13) on opposite sides of thestrip material (15), and at least one advance roller (13) ismotor-driven.
 15. Bending device from one of the preceding claims,wherein a cutting unit is furnished.
 16. Bending device from one of thepreceding claims, wherein a reader (5) is furnished, and the readersends signals to the controls for the bending device (1) depending onmarkings on the strip material (15).